BRUSSELS — Prime Minister Haider al-Abadi of Iraq appealed for help on Wednesday in training his military and reconstructing towns and cities that Iraq hopes to wrest from the Islamic State’s control.

Mr. Abadi outlined the requests after having arrived here for a meeting of nearly 60 nations on ways to counter the militants from the Islamic State, also known as ISIS or ISIL.

American officials said that the cost of the reconstruction had yet to be determined. But it is most likely to be substantial if Iraqi forces succeed in retaking Mosul, Falluja and other populated areas in street fighting that could be prolonged and bloody.

In a news conference Wednesday, Secretary of State John Kerry said that Mr. Abadi had “put the topic of reconstruction on the table.” But Mr. Kerry expressed hope that Saudi Arabia and other oil-rich Arab states might bear most of the cost.

“I don’t think this is something where Americans and Europeans or others have to recoil and say, ‘Oh my God, we are going to be facing this monumental task of rebuilding yet another place,’ ” Mr. Kerry said. “Might we have to contribute to it? Sure. We ought to. It’s part of our foreign policy.”

Mr. Kerry, who presided over the meeting at NATO’s headquarters here, insisted that the American-led airstrikes had damaged the Islamic State’s logistical capabilities and slowed its momentum. But Mr. Kerry acknowledged that the campaign against the militants might be prolonged.

“Our commitment will be measured most likely in years,” he said.

While American officials say that the airstrikes have made it more difficult for the Islamic State to mass large numbers of forces and travel in convoys, there is no indication that the militants have lost their ardor for fighting, and there are still many of them.

American military and intelligence officials have confirmed reports that Iran had carried out bombing raids in support of Iraqi forces in recent days.

Mr. Abadi, in a brief comment to reporters here, insisted that he had no knowledge of the airstrikes.

Mr. Kerry said that the United States did not intend to directly coordinate its military operation in Iraq with Iran, but he described a procedure that appeared to amount to an indirect way to ensure that American and Iranian airstrikes did not conflict.

“We are obviously flying our missions over Iraq, and we coordinate those missions with the Iraqi government,” Mr. Kerry said. “And we rely on the Iraqi government to deconflict whatever control of their air space may in fact need that deconfliction.”

Mr. Kerry added, “I think it’s self-evident that if Iran is taking on ISIL in some particular place, and it’s confined to taking on ISIL and it has an impact, it’s going to be — the net effect is positive. But that’s not something that we’re coordinating.”

Under plans approved by President Obama, 3,000 American troops will advise Iraqi forces and train new units.

Video

As this 2014 video explains, the United States targeted ISIS' oil refineries as a way to cripple the terrorist group's economy. But the oil smuggling routes themselves have been around for decades.Published OnDec. 1, 2014CreditImage by Karim Sahib/Agence France-Presse — Getty Images

Iraq security forces are planning a major offensive in the spring against the Islamic State. The goal is to restore the Iraqi government’s control over major population centers in northern and western Iraq and its border with Syria by the end of 2015.

American officials have said that the initial Iraqi force it is now advising will consist of only nine Iraqi brigades and three similar Kurdish pesh merga units, which is roughly 24,000 troops. The Iraqi plan calls for at least doubling that force before mounting the offensive.

In his meeting with Jens Stoltenberg, NATO’s secretary general, Mr. Abadi asked for additional help in building up Iraq’s fighting ability against the Islamic State.

“The prime minister informed him that Iraq is sending a request to NATO for defense capacity building support,” said Oana Lungescu, a spokeswoman for Mr. Stoltenberg.

“Once received, this request will be reviewed by the by the North Atlantic Council,” Ms. Lungescu added, referring to NATO’s main decision-making body.

NATO was involved in training Iraqi forces inside Iraq during the American occupation, but that role ended when American troops were withdrawn in 2011.

A NATO official, who asked not be identified because the official was discussing internal planning, said that any new alliance program “would need to be complementary to the considerable efforts already undertaken by the U.S.-led coalition and individual NATO allies.”

In meetings with American and other officials, Mr. Abadi also said that Iraq had a pressing need for reconstruction and humanitarian aid to help displaced civilians get through the winter.

“It won’t do any good, obviously, if you simply reclaim a town and the folks in that town have worse or less opportunities than they may have had before and life is even harder,” Mr. Kerry said.

A version of this article appears in print on , on Page A16 of the New York edition with the headline: Iraq’s Leader Requests More Aid in Fight Against ISIS. Order Reprints | Today’s Paper | Subscribe